Compound sawtooth in EAST LHCD plasma: An experimental study

Xu, Long; Hu, Liqun; Chen, Kaiyun; Li, Miaohui

doi:10.1088/1674-1056/23/8/085201

Cited by 4 publications

(2 citation statements)

References 22 publications

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“…As mentioned in figures 5(c) and (d), the nonlinear M3D simulation predicted crash has more than one crash, which is similar in shape to the compound SC observed in many tokamaks [42][43][44][45], however, it is not compound sawtooth here, compound sawtooth consists with more than two crashes in experiment, and the simulation here is a complex crash process only. We now investigate the complex crash process in detail.…”

Section: M3d Nonlinear Simulation Resultssupporting

confidence: 65%

Magnetohydrodynamics-induced internal crash near density limit in ohmic discharge on experimental advanced superconducting tokamak

Xu¹,

Duan²,

Shen³

et al. 2020

Phys. Scr.

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The magnetohydrodynamics (MHD)-induced internal crash (IC) is one of the most fundamental dynamics of a tokamak discharge. Study of IC and the consequent formation of seed island (for neo-classical tearing modes) are still attractive in both experimental and numerical studies. In this work, a set of MHD-induced sawtooth like crashes (SLCs) have been observed in experimental advanced superconducting tokamak (EAST) ohmic discharge near density limit. With the tomography of high-resolution upgraded soft x-ray imaging system, it is observed that m/n = 2/1 tearing mode converts to a m/n = 1/1 instability, and it then triggers crash in the plasma core, here, m is the poloidal mode number and n is the toroidal mode number. Similar to sawtooth crash (SC), the crash of SLC here is due to m/n = 1/1 mode nonlinear dynamic. An extended MHD simulation code M3D is used to understand of the dynamics of m/n = 1/1 internal kink mode in SC in torus. A complex SC is reproduced from M3D nonlinear simulation under EAST realistic magnetic flux equilibrium and experimental resistivity. The rapid growth of unstable m/n = 1/1 kink and interaction with its higher harmonics, are responsible for SC. The simulation results show an existence of annular chaos belt outside q = 1 surface during SC. Furthermore, magnetic islands with higher poloidal mode number are found after SC. The formation of island after SC make plasma current profile flat in the core.

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Section: M3d Nonlinear Simulation Resultssupporting

confidence: 65%

Magnetohydrodynamics-induced internal crash near density limit in ohmic discharge on experimental advanced superconducting tokamak

Xu¹,

Duan²,

Shen³

et al. 2020

Phys. Scr.

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“…This article briefly introduces some diagnostic systems which are used to analyze the magnetohydrodynamic (MHD) instabilities. The soft X-ray systems [21] with three soft X-ray cameras covering the entire plasma poloidal cross-section have been installed on EAST to measure the spectrum of soft X-ray emission, and then obtain the electron temperature and the content of some heavy impurities. The soft X-ray arrays have good enough time resolution for studying the MHD instabilities of the core plasma.…”

Section: The Description Of East and Nbi Systemmentioning

confidence: 99%

Fishbone Mode Excited by Deeply Trapped Energetic Beam Ions in EAST

Zheng

et al. 2016

Plasma Sci. Technol.

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This paper describes the fishbone mode phenomena during the injection of highpower neutral beams in EAST (Experimental Advanced Superconducting Tokamak). The features of the fishbone mode are presented. The change in frequency of the mode during a fishbone burst is from 1 kHz to 6 kHz. The nonlinear behavior of the fishbone mode is analyzed by using a prey-predator model, which is consistent with the experimental results. This model indicates that the periodic oscillations of the fishbone mode always occur near the critical value of fast ion beta. Furthermore, the neutral beam analysis for the discharge is done by using the NUBEAM module of the TRANSP code. According to the numerical simulation results and theoretical calculation, it can be concluded that the fishbone mode is driven by the deeply trapped energetic beam ions in EAST.

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Non-linear dynamics of compound sawteeth in tokamaks

et al. 2016

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Compound sawteeth is studied with the XTOR-2F code. Non-linear full 3D magnetohydrodynamic simulations show that the plasma hot core is radially displaced and rotates during the partial crash, but is not fully expelled out of the q = 1 surface. Partial crashes occur when the radius of the q = 1 surface exceeds a critical value, at fixed poloidal beta. This critical value depends on the plasma elongation. The partial crash time is larger than the collapse time of an ordinary sawtooth, likely due to a weaker diamagnetic stabilization. This suggests that partial crashes result from a competition between destabilizing effects such as the q = 1 radius and diamagnetic stabilization.

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Compound sawtooth in EAST LHCD plasma: An experimental study

Cited by 4 publications

References 22 publications

Magnetohydrodynamics-induced internal crash near density limit in ohmic discharge on experimental advanced superconducting tokamak

Magnetohydrodynamics-induced internal crash near density limit in ohmic discharge on experimental advanced superconducting tokamak

Fishbone Mode Excited by Deeply Trapped Energetic Beam Ions in EAST

Non-linear dynamics of compound sawteeth in tokamaks

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